A fiber-reinforced plastic (FRP) is a material produced by binding reinforcing fibers (e.g., glass fibers and carbon fibers) using a resin. The FRP is a composite material that exhibits excellent mechanical strength, heat resistance, formability, and the like. Therefore, the FRP is widely used in a wide variety of fields including the airplane industry, the space industry, the vehicle industry, the building material industry, the sports industry, and the like.
In particular, a carbon fiber-reinforced plastic (CFRP) is characterized by high strength and reduced weight. For example, a thermosetting epoxy resin is mainly reinforced using carbon fibers, and is used as a structural material for producing an airplane. In recent years, an FRP that utilizes a thermoplastic resin has attracted attention since the forming (molding) cycle can be reduced, and such an FRP can be recycled.
There is a tendency that the strength of a fiber-reinforced plastic depends largely on the dispersion state of the reinforcing fibers. Therefore, the strength of a fiber-reinforced plastic has been increased by increasing the content of the reinforcing fibers. For example, Patent Literature 1 discloses a cellulose fiber-containing polyolefin-based composition that includes cellulose fibers having a predetermined average fiber diameter, and a modified olefin-based polymer. Patent Literature 2 discloses a rubber composition that is obtained by mixing and drying a rubber latex and a slurry, the slurry being prepared by dispersing modified cellulose nanofibers in water, and adding a silane coupling agent to the dispersion. Patent Literature 3 discloses a fiber-reinforced composition that is prepared by dispersing modified resin particles in a matrix resin that includes a plurality of resins, and includes a fibrous filler. Patent Literature 4 discloses a reinforced polyolefin composition that includes a polyolefin resin, a modified polyolefin resin, and glass fibers that have been treated with a sizing agent that includes an aminosilane-based coupling agent.